Balance Sheet Components Other Current Assets (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Other Current Assets [Line Items]
Prepaid expenses	$ 51	$ 37
Current deferred income tax asset	38	51
Assets from price risk management activities	11	4
Other	5	1
Other current assets	$ 105	$ 93

Amount after allocation of valuation allowances of deferred tax asset attributable to deductible temporary differences and carryforwards expected to be realized or consumed within one year or operating cycle, if longer.

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The total of the amounts paid in advance for capitalized costs that will be expensed with the passage of time or the occurrence of a triggering event, and will be charged against earnings within one year or the normal operating cycle, if longer, and the aggregate carrying amount of current assets, as of the balance sheet date, not separately presented elsewhere in the balance sheet. Current assets are expected to be realized or consumed within one year (or the normal operating cycle, if longer).

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